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Background: Although IPF mortality in clinical trials appears to be of 8-10% in the first year of observation, predicting progression remains a challenging task. Aim of the study: To build a mortality prediction model by means of a previously validated 6 MWT derived index, O2-Gap*, in a cohort of anti-fibrotic naive IPF patients and to test it on a population treated according to a fixed protocol. Methods: Clinical data and the O2-Gap calculated upon an equation incorporating 6MWT duration, O 2 saturation, distance walked as % predicted (age, gender, height, weight) and SpO 2 recovery time, were retrospectively analyzed in a group of 52 patients with an 18 months follow up to build a mortality prediction model using Cox survival analysis and ROC analysis. The model was then applied to a group of pirfenidone (PF)-treated patients (n=49, mean follow up 14,7 months). Results: Observed mortality was 40.4% in the derivation population, with a death RR of 1.4 (CL95% 1.1-1.8) per unit of O2-Gap. With a O2-Gap threshold of 3.2 the test showed sensitivity and specificity values of 62% and 77.4% (area under the ROC curve: 77.5 CI95% 64.5-90.4). Consistent with the model, IPF treated patients with O2-GAP >3 showed an increased mortality rate (n=15, 9 deaths=60%,) compared to those with a Conclusions: Even with the limitation of the small population, this study indicates the O2-Gap, a simple index that can be automatically calculated on an electronic pulse-oxymeter, as a strong mortality predictor and a potentially useful clinical tool, once validated in larger cohort studies. *Patent # PCT/IT2010/000361. |
